[单项选择]

I want to talk today about some studies. They seem to indicate that there is a startling world-wide decline in the number of amphibians, such as frogs, toads and salamanders. There’s little doubt that one reason why the number of amphibians is declining is their habitats have been destroyed when the developers fill in ponds and marshes to build houses. Amphibians can’t just move somewhere. They need water to lay their eggs in. Another problem is the growing fish industry. Another range of popular pool fish such as carp have been introduced to many lakes and ponds all over the world. Raising and selling these fish can be profitable, but the fish eat the eggs and offspring of amphibians that were already living in the lakes and ponds. Other factors could be contributing to the decline include acid rain and the spread of pesticide residues. Many pesticides that farmers added to their crops are eventually washed away by the rain and end up in ponds and other bodies of wat
A. By taking over ponds.
B. By constructing sewers.
C. By building dams on rivers.
D. By flooding marshes.

I want to talk today about some studies. They seem to indicate that there is a startling world-wide decline in the number of amphibians, such as flogs, toads and salamanders. There’s little doubt that one reason why the number of amphibians is declining is their habitats have been destroyed when the developers fill in ponds and marshes to build houses. Amphibians can’t just move somewhere. They need water to lay their eggs in. Another problem is the growing fish industry. Another range of popular pool fish such as carp have been introduced to many lakes and ponds all over the world. Raising and selling these fish can be profitable, but the fish eat the eggs and offspring of amphibians that were already living in the lakes and ponds. Other factors could be contributing to the decline include acid rain and the spread of pesticide residues. Many pesticides that farmers added to their crops are eventually washed away bythe rain and end upin pondsand other bodies of water
A. The distribution of different species of amphibians.
B. Possible reasons for reduction in the number of amphibians.
C. The effects of environmental change on the fish industry.
D. Guidelines for the responsible use of pesticides.

Today I want to talk about levels of language usage. You probably have noticed that people express similar ideas in different ways, depending on the situation they are in. This is very natural. All languages have two general, broad categories, or levels of usage: a formal level and an informal level. English is no exception. I’m not talking about correct and incorrect English. What I’m talking about are two levels of correct English. The difference in these two levels is the situation in which you use a particular level. Formal language is the kind of language you find in textbooks, reference books such as encyclopedias, and in business letters. For example, a letter to a university would be in formal style. You would also use formal English in compositions and essays that you write in school. People usually use formal English when they give classroom lectures or speeches and at ceremonies such as graduations. We also tend to use formal language in conversations with